1. Field of the Invention
A hopper loader, also known as a shot hopper, for processing machines such as molding machines is provided which is particularly useful in supplying particulate material to a molding machine, such as an injection molding machine. The hopper loader hereof includes a housing designed to advantageously accommodate particulate material of different sizes and promotes efficient usage by utilizing a transparent hopper and the configuration of the filter element.
2. Description of the Prior Art
Hopper loaders, and particularly hopper loaders of the shot hopper type, are used in conjunction with processing machines. A “shot” refers to one cycle of a molding machine, and thus a shot hopper is designed to hold and deliver a sufficient quantity of material to complete one cycle of a molding machine. An exemplary use of a hopper loader is to accumulate and then deliver synthetic resin particulate material, for example polyethylene, to molding machines. These molding machines receive the synthetic resin particulate material from the hopper loader, heat the synthetic resin to a desired temperature to melt the resin and then force it into molds. When cooled, the resin forms useful articles. The synthetic resin particulate material is typically delivered to the hopper loader by pneumatic means whereby a quantity sufficient to supply the molding machine or other processing equipment remains on hand, providing a supply of raw material for processing in a mode suited to the machine.
In most instances, the hopper loader may readily handle particulate material which is relatively uniform and has not previously processed. For example, in the case of injection molding machines, synthetic resin (also known as “plastic”) which has not previously been used in the molding process is relatively uniform and easy to convey and process. This so-called “virgin plastic” is typically provided in pellet form and is to be contrasted with what is known in the industry as “regrind.” Regrind plastic is, for example, polyethylene which has either been recovered from waste or scrap after processing through a molding machine or from recycled articles and ground into a flake. In either case, regrind plastic may be re-used in the molding process, but as noted is typically of a different particulate size or character. As such, it is typical to reprocess regrind plastic with virgin plastic in a mixture delivered to a hopper loader, rather than to use only regrind plastic in molding an article.
The combination of virgin and regrind plastic is often more difficult to process through a processing machine, such as a molding machine, particularly at the hopper loader. This combination of virgin and regrind plastic has a tendency to clog inside conventional hopper loaders. Heretofore, conventional hopper loaders have not heretofore been capable of handling 100% regrind or even a majority of regrind in a mix of regrind and virgin plastic. Even in mixes of virgin plastic and regrind at lower proportions of regrind, significant downtime and maintenance is required to deal with such clogging, and to maintain a necessary volume of material within the hopper to be processed. Another problem which has been encountered is the particulate material entrained in the air which conveys it to the loader, with difficulty in handling the air which must be filtered to remove the particulate before being exhausted to the atmosphere.
As a consequence, there has developed a need for an improved hopper loader which addresses these and other problems.